Research On Multirate Multicast Congestion Control Algorithms

Recently, multimedia applications take a growing place in the Internet. If multiple users want to receive the same multimedia data at the same time, multicast is the most efficient way of one-to-many transmission. In traditional multicasting, all receivers of the same multicast group receive data at the same rate. However, the Internet's intrinsic heterogeneity and diverse receivers make single-rate multicast unsuitable. For single-rate multicast is likely to overwhelm the slow receivers and starve the fast ones. Thus, multirate multicast, where the receivers of the same multicast group can receive data at different rates commensurate with their diverse requirements and also with the capacity of the path leading to it from the source, has received a great deal of attention, especially in video application. The main problem of multirate multicast research is multirate multicast congestion control algorithm.In this paper, we focus on the research of multirate multicast congestion control algorithms. First, we introduce two metrics to evaluate multirate multicast congestion control algorithms: fairness and scalability, then we analyze and discuss three kinds of multirate multicast congestion control algorithms, finally, we propose a new multirate multicast congestion control algorithm aiming at improving the global video quality.This new algorithm is an improvement over a receiver-driven, source adaptive algorithm, mainly over optimization objective of source layer rate adjusting. Considering the diversity of applications, we introduce a global quality index (GQI) that characterizes the density of satisfied receivers, the amount of allocated network bandwidth and the stability of the quality of the receivers. Then we formulate the optimal layer rate allocation problem with the objective of minimizing this index and derive an efficient algorithm to solve the problem, simulation results demonstrate that using this index, the users' objective can be achieved.